Economic thought may be roughly divided into three phases: Premodern (Greek, Roman, Arab), Early modern (mercantilist, physiocrats) and Modern (since Adam Smith in the late 18th century). Systematic economic theory has been developed mainly since the birth of the modern era.

Several ancient philosophers made various economic observations. Among them Aristotle is probably the most important.

Mediaeval Arabs also made contributions to the understanding of economics. In particular, Ibn Khaldun of Tunis (1332-1406) wrote on economic and political theory in his Prolegomena, showing for example, how population density is related to the division of labour which leads to economic growth and so in turn to greater population in a virtuous circle.

The physiocrats were soon overshadowed by Adam Smith's Wealth of Nations[?], published in 1776. Today it is customary to consider Smith the founder of economic theory - and the classical economics that developed after him to be the beginnings of formal economic study.

The history of the various schools of thought in economics can be loosely categorised as follows:

Neoclassical economics dominates in undergraduate textbooks. The core of contemporary economics rests on the microeconomic theory of neoclassical economics, but on many topics there is little agreement on which schools to develop to usefully explain existing economies. Outside mainstream economics more widely-divergent views abound.

Throughout the history of economic thought, different political ideas have often been associated with different schools of thought about how economies operate. For example, Adam Smith used his theories of trade and of the division of labour to argue for laissez-faire government economic policies, particularly against mercantilism. Similarly, Marx developed his theories, which focus on production and labor, to advocate socialism and communism.

An example of another economic system which has recently been advocated is the participatory economics model. This uses neither market methods nor centralised methods for allocation, but incorporates many local positive and negative feedback loops in order to respond to the most positive human values. In "-ist" terminology, the participatory economics model is neither communist nor capitalist.